1. Field of the Invention
The present invention relates to placement of frequency converters, especially the power units of frequency converters in a switch cabinet or equivalent. In particular, the invention relates to encasement of frequency converters provided with separate power and control units, wherein the power units contain the frequency converter's power stage including power semiconductor switches and the control units contain the required control electronics. The invention also relates to placement of frequency converters provided with a small-size power unit in a switch cabinet or equivalent.
2. Description of the Background Art
Frequency converters are placed in switch cabinets when they are so large that no other type of encasement is appropriate. Frequency converters are also generally placed in a cabinet when the same delivery to a customer comprises several frequency converters (line and group drives), in which case the cabinet functions from the user's point of view as a protection against contact and as a uniform exterior face. As for the units themselves, placement in a cabinet protects them e.g. from water and dust.
Usually one bay in the cabinet is used to accommodate one frequency converter and different bays are interconnected by a set of AC or DC rails e.g. as shown in FIG. 1. FIG. 1 presents three frequency converters FC#11–FC#13, each placed in a separate bay 11–13 in the cabinet. The supply voltage to the frequency converters is normally obtained from a set of power busbars 16 which runs through all the bays and which may be installed e.g. in the upper part of the cabinet. The cables 17 to the motors are normally led downwards from the cabinet. Cooling air is normally passed from below upwards, circulated by a frequency converter-specific fan. The air is most commonly taken through grids mounted in the lower part of the cabinet or through the bottom of the cabinet and removed via the upper part of the cabinet either through the door or through the ceiling.
When there is a need to implement the cabling or air flow in some other way differing from that described above, a considerably large space may be required. For example, if the motor cable has to be led upwards or if supply air is obtained from above piping, it may be necessary to add extra bays 14, 15 as shown in FIG. 2, through which the cabling or air can be arranged to be passed.